The present invention concerns a device for changing the timing of intake and exhaust valves in an internal combustion engine according to the features in the present invention, which is especially advantageous for hydraulic camshaft adjustment mechanisms.
Such a device is already generically known from German Patent Publication DE 197 45 670 A1. This device, essentially designed as a hydraulic servo-drive, is positioned at the drive-side end of a camshaft supported in the cylinder head of an internal combustion engine and consists of one component driven together with a crankshaft of the internal combustion engine as well as of another component rotationally connected with the camshaft. The camshaft-coupled component is hydraulically rotatable and lockable with respect to the crankshaft-coupled component and thus effects a relative rotation or a hydraulic clamping of the camshaft with respect to the crankshaft. The supply and withdrawal of hydraulic fluid to and from the device proceeds via a cylindrical hydraulic-fluid adapter positioned on the device""s axial side facing away from the camshaft and attached to the camshaft-coupled component. This adapter includes several hydraulic-fluid lines running in the axial, radial, and circumferential direction and is supported in a sleeve bearing in the cylinder head of the internal combustion engine. The sleeve bearing is connected with the hydraulic-fluid circuit and is designed at the same time as the radial bearing of the camshaft. In addition, there is attached to the end wall of the hydraulic-fluid adapter, facing away from the camshaft, an impulse-sending wheel which cooperates with a suitable impulse-reading device and together with the latter serves in determining the camshaft position with respect to the crankshaft position during operation of the internal combustion engine.
In this known solution, however, it is disadvantageous that the required axial support of the camshaft connected with the device must be formed by a separate axial bearing on the camshaft so that precise machining of the camshaft and thus relatively high production costs are involved in its manufacture. In addition, such an axial bearing requires in connection with the impulse-sending wheel attached to the device an increased overall axial length of the camshaft and thus of the total cylinder head of the internal combustion engine, which, however, is frequently not possible due to the usually very restricted space conditions in the engine compartment of the vehicle.
The present invention is directed to providing a device for changing the timing of intake and exhaust valves in an internal combustion engine in which the high production costs for an axial bearing on the camshaft as well as the overall axial length of the camshaft necessary for this axial bearing and for the impulse-sending wheel attached to the device can be reduced to a minimum.
This problem is solved according to the present invention for a device for changing the valve timing of an internal combustion engine by providing the hydraulic-fluid adapter on its end wall facing away from the camshaft with a diametrically expanded end flange which, on the one hand, simultaneously forms the impulse-sending wheel of the device and, on the other hand, is designedxe2x80x94together with a washer positioned between the hydraulic-fluid adapter and the component coupled to the camshaft and likewise diametrically enlarged with respect to the hydraulic-fluid adapterxe2x80x94as the axial bearing of the camshaft.
Alternatively, it is also possible to form the part of the axial bearing of the camshaft by the washer through a spacing ring fashioned on the axial side of the camshaft-coupled component facing away from the camshaft or through another diametrically expanded end flange positioned on the end wall of the hydraulic-fluid adapter facing the camshaft.
In appropriately refining this device according to the present invention, it is still further proposed that one can additionally position the head of the axial fastening bolt of the device at least partially in a countersink in the end wall of the hydraulic-fluid adapter facing away from the camshaft in order to still further reduce the overall axial length of the camshaft designed with the device. Proving especially advantageous here is the use of a fastening bolt having a hexagonal-socket-head which includes a diametrically enlarged collar and is positioned over about half of its axial length in the countersink of the hydraulic-fluid adapter.
The impulse-sending wheel formed by the end flange on the hydraulic-fluid adapter is designed in this case as a flat ring-shaped disk whose impulse marks are formed by notches or boreholes or the like distributed symmetrically or asymmetrically around its periphery or on its axial side and which cooperates with an impulse-reading device secured to the internal combustion engine and positioned axially to it.
It is also possible to solve the problem lying at the basis of the present invention involving a device for changing the timing of intake and exhaust valves by providing the impulse-sending wheel of the device attached to the end wall of the hydraulic-fluid adapter facing away from the camshaft with a greater diameter than the hydraulic-fluid adapter andxe2x80x94together with a washer positioned between the adapter and the camshaft-coupled component and likewise diametrically enlarged with respect to the hydraulic-fluid adapterxe2x80x94is simultaneously designed as the axial bearing for the camshaft.
In this case, it is also alternatively possible to form the part of the axial bearing of the camshaft formed by the washer through a spacing ring fashioned on the axial side of the camshaft-coupled component facing away from the camshaft or through a diametrically enlarged end flange positioned on the camshaft-facing end wall of the hydraulic-fluid adapter, as in the above-described embodiment.
As an appropriate refinement of the device according to the present invention, it is also possible to provide the impulse-sending wheel preferably as a cup-shaped sheet-metal piece which is separately attached by an additional nut to the head of the axial fastening bolt of the device such that it radially surrounds this nut. This special attachment of the impulse-sending wheel to the device has proven to be especially advantageous with regard to its consequently possible separate adjustability during assembly of the device to the camshaft of the internal combustion engine since then, with initially only lightly tightened fastening bolt, the required starting position of the camshaft-coupled component or the camshaft to the crankshaft-coupled component or the crankshaft can be adjusted and subsequently, with fully tightened fastening bolt, the impulse-sending wheel can be separately suitably adjusted. However, it would also be possible to secure the impulse-sending wheel to the hydraulic-fluid adapter with the axial fastening bolt of the device and to carry out simultaneously the adjustment of the camshaft-coupled component with respect to the crankshaft-coupled component of the device as well as the adjustment of the impulse-sending wheel. In the same way, it is also possible with the device according to the present invention to design the impulse-sending wheel as a flat ring-shaped disk and/or to position the head of the axial fastening bolt at least partially in a countersink in the hydraulic-fluid adapter in order to reduce the overall axial length of the camshaft designed with the device.
The preferably cup-shaped impulse-sending wheel of this device is provided as part of the axial bearing of the camshaft, which can also be fashioned with the same arrangement and action like a spoked wheel with angled spoke ends on the peripheral side, and furthermore includes at its periphery symmetrically or unsymmetrically distributed impulse marks designed as notches, boreholes, or the like and cooperates in this case with an impulse-reading device secured to the internal combustion engine and positioned radially to it.
Both of the devices according to the present invention thus exhibit, compared to the device known from the state of the art, the advantage that as a result of the integration of the axial bearing of the camshaft or the axial bearing of the camshaft and the impulse-sending wheel of the device in the components present in the device, it is no longer necessary to provide a special axial bearing for the camshaft. As a result, the production costs of a camshaft provided with such a device are considerably reduced in advantageous fashion. At the same time, the overall axial length of camshafts provided with these devices is reduced such that the devices of the present invention can also be used in internal combustion engines with very restricted space conditions in the engine compartment of the motor vehicle.